Sliding component

ABSTRACT

A positive pressure generating mechanism comprising a positive pressure generating groove is provided to a high-pressure side of one of two sliding surfaces that slide relative to each other in a pair of sliding components, and a negative pressure generating mechanism comprising a negative pressure generating groove is provided to a low-pressure side. The positive pressure generating groove and negative pressure generating groove are communicated with a high-pressure fluid side and separated from a low-pressure fluid side by a seal surface.

TECHNICAL FIELD

The present invention relates to a sliding component applied to amechanical seal, a bearing, or another sliding part, for example. Thepresent invention particularly relates to a sliding component of asealing ring, a bearing, or the like, in which a fluid is present onsliding surfaces to reduce friction, and the fluid must be preventedfrom leaking out from the sliding surfaces.

BACKGROUND ART

In a mechanical seal, which is one example of a sliding component, thecontrary conditions “sealing” and “lubrication” must both be achieved inorder to maintain airtightness over a long period of time. Particularly,in recent years there has been a rising demand for less friction inorder to prevent leakage of sealed fluid and reduce mechanical loss, forthe sake of environmental measures and the like. The means of reducingfriction can be achieved by creating a so-called fluid lubricationstate, in which dynamic pressure is generated by rotation betweensliding surfaces and sliding occurs in the presence of a liquidmembrane. However, in this case, positive pressure is generated betweenthe sliding surfaces, and the fluid flows out of the sliding surfacesfrom the positive pressure portion. This is known as lateral leakage ina bearing, and is equivalent to the leakage in the case of a seal. Thesealed fluid is located on the external peripheral side of the sealsurface, the atmosphere is located on the internal peripheral side, andthe internal-peripheral-side leakage rate when the fluid on the externalperipheral side is scaled (known as the “inside type”) is expressed bythe following formula.

$\begin{matrix}{Q = {- {\int{\left( \left. {\frac{h^{3}}{12\eta}\frac{\partial p}{\partial r}} \right|_{r = \eta} \right){r_{1} \cdot {\theta}}}}}} & \left\lbrack {{Formula}\mspace{14mu} 1} \right\rbrack\end{matrix}$

Q: internal-peripheral-side leakage rate in sliding surface insidediameter r1

h: gap height

η: fluid viscosity

p: pressure

It is clear from the above formula that as fluid lubrication ispromoted, dynamic pressure is generated, and a liquid membrane isformed; the pressure gradient ∂p/∂r on the internal peripheral end sideincreases, h increases, and as a result, the leakage rate Q increases.

Consequently, to reduce the leakage rate Q in the case of a seal, thegap h and the pressure gradient ∂p/∂r must be reduced.

From the above matters, in a conventional seal, a so-called compromiseof sealing and lubrication, in which sealing performance is maintained,is achieved by reducing the liquid membrane thickness h to an extentthat does not damage the sliding surfaces.

Consequently, in a seal used in an environment where contact causesimmediate surface damage such as scorching, the result of prioritizingthe dynamic pressure effect is that the liquid membrane thickness hincreases and the leakage rate therefore increases. In a seal used in anenvironment in which direct contact does not readily cause problems evenover a long period of time, the result of prioritizing sealingperformance is that the gap h is small, the dynamic pressure effect isalso small, and there is therefore a higher possibility of surfaceabrasion or damage due to direct contact, and a higher frictionalcoefficient. An example of the former structure is the inventiondisclosed in Patent Document 1, for example. This invention is a dry gasseal but can also be applied to a liquid seal, and although an excellentdynamic pressure effect is obtained, the leakage rate is extremely high.An example of the latter structure is a structure in which calcinedcarbon having excellent self-lubrication in a stationary ring side isused so that problems are unlikely to occur even with direct contact,and flat surfaces are sealed together. In another example, undulation ora spiral groove is implemented as a dynamic pressure generatingmechanism (see Patent Documents 2 and 3, for example).

In a liquid seal, since viscosity is higher than gas, the dynamicpressure effect is obtained by the unevenness of minute asperities orroughness of the surfaces, even if the surfaces are flat. Therefore,structures that prioritize sealing performance are often used. Toachieve both sealing and lubrication, a number of structures have beenproposed which have a pumping effect of drawing leaked liquid back tothe high-pressure side. Patent Document 4, for example, discloses amechanism in which pumping is achieved by shear flow, due to a “barrier”of a different height being set up in advance between two rotating orstatic surfaces separated by a gap. In this mechanism, the structure iscomplicated because an initial gap must be provided mechanically, andsince the gap is also present when no motion is occurring, a problem isencountered in that leakage occurs when no motion is occurring.

Non-patent Document 1 discloses a structure in which ahigh-pressure-side fluid is temporarily retained in a dam part, andafter dynamic pressure is generated in a Rayleigh step bearing part, thefluid is returned to the high-pressure side. In this structure, sincedynamic pressure is not generated until the liquid is retained in thedam part, sliding occurs along with direct contact immediately afterrotation starts, and accordingly there is a risk of surface damageoccurring during this time.

Furthermore, Non-patent Document 2 discloses a proposal of creating apumping effect using a shear flow during rotation, due to a pumpinggroove being set up on the upstream side of a Rayleigh step. In thismechanism, a problem is encountered in that leakage occurs when nomotion is occurring because a high-pressure side and a low-pressure sideare joined by the pumping groove.

The present applicant has submitted for application, as an inventionrelating to a sliding component, an invention in which a sealed fluid isled into a sliding surface by suction means formed on a sealed fluidside of the sliding surface, and the led-in sealed fluid is stored via adam part in two dimple parts formed in the sliding surface, one on aradially external peripheral side and one on a radially internalperipheral side, while the sealed fluid is simultaneously pumped in thedimple part on the radially internal peripheral side; whereby the sealedfluid is prevented from leaking out from a seal surface positionednearer the radially internal peripheral side than the two dimple parts(see Patent Document 5). In this invention, among the two dimple parts,a pumping action is created in the dimple part on the radially internalperipheral side to prevent the sealed fluid from leaking out from theseal surface, but the dimple part on the radially internal peripheralside forms a closed space and therefore has no negative pressure.Therefore, it is not possible to prevent leakage of the fluid present onthe sliding surface that is nearer the radially internal peripheral sidethan the dimple part. Specifically, it is possible to prevent leakage toa certain extent, but an increase in the leakage rate cannot be avoided.

As described above, there is no conventional technique for achievingboth sealing and lubrication wherein there is no leakage when no motionis occurring, and during rotation including the start of rotation, fluidlubrication is in effect and leakage is prevented.

PRIOR ART DOCUMENTS Patent Documents

-   Patent Document 1: JP-A 4-73-   Patent Document 2: U.S. Pat. No. 5,071,141-   Patent Document 3: U.S. Pat. No. 7,377,518-   Patent Document 4: JP-A 58-42869-   Patent Document 5: JP-A 2005-180652

Non-Patent Documents

-   Non-patent Document 1: Transactions of ASME Journal of Tribology    Vol. 107, JULY 1985 p. 326-322 “A Zero-Leakage Film Riding Face    Seal” A. Lipschitz-   Non-patent Document 2: Japan Society of Mechanical Engineers    Collection (Edition C) Vo. 53 No. 493, September 1987 p. 2017-2024    “A Face Seal with Circumferential Pumping Grooves and    Rayleigh-Steps” Takeshi Ikeuchi, Haruo Mori, Tohru Nishida

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

An object of the present invention is to provide a sliding componentwherein there is no leakage when no motion is occurring, fluidlubrication is in effect and leakage is prevented during rotationincluding the start of rotation, and both sealing and lubrication can beachieved.

Means for Solving these Problems

A first aspect of the sliding component of the present invention forachieving the object described above is characterized in that a negativepressure generating mechanism comprising a negative pressure generatinggroove is provided to a low-pressure side of one of two sliding surfacesthat slide relative to each other in a pair of sliding components, thenegative pressure generating groove being communicated with ahigh-pressure fluid side via a radial-direction groove and separatedfrom a low-pressure fluid side by a seal surface.

According to the first aspect, there is no leakage when no motion isoccurring, the pressure gradient ∂p/∂r in the end of the low-pressureside of the sliding surface (e.g., the seal internal peripheral side inthe case of an inside-type mechanical seal) can be made negative duringusual times including the start of relative sliding, and a pumpingaction occurs from the low-pressure side of the sliding surface towardthe high-pressure fluid side; therefore, the leakage rate can besignificantly reduced.

A second aspect of the sliding component of the present invention ischaracterized in that a positive pressure generating mechanismcomprising a positive pressure generating groove is provided to ahigh-pressure side of one of two sliding surfaces that slide relative toeach other in a pair of sliding components, and a negative pressuregenerating mechanism comprising a negative pressure generating groove isprovided to a low-pressure side, the positive pressure generating grooveand negative pressure generating groove being communicated with ahigh-pressure fluid side and separated from a low-pressure fluid side bya seal surface.

A third aspect of the sliding component of the present invention ischaracterized in that appositive pressure generating mechanismcomprising a positive pressure generating groove is provided to ahigh-pressure side of one of two sliding surfaces that slide relative toeach other in a pair of sliding components, and a negative pressuregenerating mechanism comprising a negative pressure generating groove isprovided to a low-pressure side of the other sliding surface, thepositive pressure generating groove and negative pressure generatinggroove being communicated with a high-pressure fluid side and separatedfrom a low-pressure fluid side by a seal surface.

A fourth aspect of the sliding component of the present invention ischaracterized in that an external peripheral side of a pair of slidingcomponents is a high-pressure fluid side and an internal peripheral sideis a low-pressure fluid side, a positive pressure generating mechanismcomprising a positive pressure generating groove is provided to ahigh-pressure side of a sliding surface of a stationary-side slidingcomponent, and a negative pressure generating mechanism comprising anegative pressure generating groove is provided to a low-pressure sideof a sliding surface of a rotating-side sliding component, the positivepressure generating groove and negative pressure generating groove beingcommunicated with the high-pressure fluid side and separated from thelow-pressure fluid side by an internal-peripheral-side seal surface.

A fifth aspect of the sliding component of the present invention ischaracterized in that a pair of sliding components comprise annularbodies, an external peripheral side of the annular bodies is ahigh-pressure fluid side and an internal peripheral side is alow-pressure fluid side; in a sliding surface on one side of the annularbody, a positive pressure generating mechanism comprising a positivepressure generating groove is provided to the external peripheral side,and a negative pressure generating mechanism comprising a negativepressure generating groove is provided to the internal peripheral side;the positive pressure generating groove and negative pressure generatinggroove being communicated with the high-pressure fluid side andseparated from the low-pressure fluid side by aninternal-peripheral-side seal surface.

A sixth aspect of the sliding component of the present invention ischaracterized in that a pair of sliding components comprise annularbodies, an external peripheral side of the annular bodies is ahigh-pressure fluid side and an internal peripheral side is alow-pressure fluid side; a positive pressure generating mechanismcomprising a positive pressure generating groove is provided to theexternal peripheral side on a stationary-side sliding surface of theannular body, and a negative pressure generating mechanism comprising anegative pressure generating groove is provided to the internalperipheral side in a rotating-side sliding surface of the annular body;the positive pressure generating groove and negative pressure generatinggroove being communicated with the high-pressure fluid side andseparated from the low-pressure fluid side by aninternal-peripheral-side seal surface.

According to the second through sixth aspects, since the slidingsurfaces operate in a state of fluid lubrication during usual timesincluding the start of relative sliding, the frictional coefficient canbe lowered, there is no leakage when no motion is occurring, thepressure gradient ∂p/∂r in the low-pressure side of the sliding surfacecan be made negative during usual times including the start of relativesliding, a pumping action occurs from the low-pressure side of thesliding surface toward the high-pressure fluid side, and the leakagerate can therefore be significantly reduced.

Furthermore, according to the third and sixth aspects, since there ismore space than in cases in which both a Rayleigh step mechanism and areverse Rayleigh step mechanism are provided to the same slidingsurface, the mechanisms are easily disposed in the sliding surfaces, andmachining time can be shortened.

Furthermore, according to the fourth aspect, the fluid used forlubrication is not susceptible to the effects of centrifugal force fromrotation, an appropriate amount of fluid can be ensured between thesliding surfaces, and a better state of fluid lubrication can thereforebe obtained.

A seventh aspect of the sliding component of the present invention isany of the second through sixth aspects, characterized in that theexternal-peripheral-side positive pressure generating mechanism isformed from a Rayleigh step mechanism, and the internal-peripheral-sidenegative pressure generating mechanism is formed from a reverse Rayleighstep mechanism, the Rayleigh step mechanism and reverse Rayleigh stepmechanism being communicated with the high-pressure fluid side via aradial-direction groove.

According to the seventh aspect, the positive pressure generatingmechanism and the negative pressure generating mechanism can be easilyprovided to the sliding surfaces of the sliding components.

An eighth aspect of the sliding component of the present invention isthe seventh aspect, characterized in that pluralities of Rayleigh stepmechanisms and reverse Rayleigh step mechanisms are provided in parallelin a circumferential direction so as to constitute pairs, and anupstream end of a groove part of an n^(th) Rayleigh step mechanism and adownstream end of a groove part of an n−1^(th) reverse Rayleigh stepmechanism are formed so as to substantially coincide in a position inthe circumferential direction as seen from the upstream side, bothgroove parts being communicated with the high-pressure fluid side viashared communication means.

According to the eighth aspect, Rayleigh step mechanisms and reverseRayleigh step mechanisms can be efficiently placed in the slidingsurfaces of the sliding components comprising annular bodies, the numberof radial-direction grooves can be reduced, and the fluid leakage ratecan therefore be reduced.

A ninth aspect of the sliding component of the present invention is theseventh aspect, characterized in that a plurality of Rayleigh stepmechanisms and one reverse Rayleigh step mechanism are provided inparallel in a circumferential direction, an upstream end of a groovepart of the Rayleigh step mechanisms and a downstream end of a groovepart of the reverse Rayleigh step mechanism are formed so as tosubstantially coincide in a position in the circumferential direction,and the groove parts are communicated with the high-pressure fluid sidevia a shared radial-direction groove, the upstream ends of the grooveparts of the remaining Rayleigh step mechanisms being individuallycommunicated with the high-pressure fluid side via individualradial-direction grooves.

According to the ninth aspect, the Rayleigh step mechanisms and thereverse Rayleigh step mechanism can be efficiently placed in the slidingsurfaces of the sliding components comprising annular bodies, the numberof shared radial-direction grooves can be kept at one, and the fluidleakage rate can therefore be minimized

A tenth aspect of the sliding component of the present invention is theseventh aspect, characterized in that a plurality of reverse Rayleighstep mechanisms are provided in a radial direction.

According to the tenth aspect, negative pressure is generatedincrementally, a structure capable of better preventing leakage isachieved, and the invention is therefore applicable to a high-pressureand high-speed seal.

An eleventh aspect of the sliding component of the present invention ischaracterized in that a positive pressure generating mechanismcomprising a spiral groove or a dimple directly communicated with ahigh-pressure fluid side is provided to a high-pressure side of one oftwo sliding surfaces that slide relative to each other in a pair ofsliding components, and a negative pressure generating mechanismcomprising a reverse Rayleigh step mechanism is provided to alow-pressure side, the reverse Rayleigh step mechanism beingcommunicated with the high-pressure fluid side via a radial-directiongroove and separated from a low-pressure fluid side by a seal surface.

According to the eleventh aspect, the positive pressure generatingmechanism can be formed from a spiral groove or a dimple.

A twelfth aspect of the present invention is characterized in that apositive pressure generating mechanism comprising a positive pressuregenerating groove is provided to a high-pressure side of one of twosliding surfaces that slide relative to each other in a pair of slidingcomponents, a negative pressure generating mechanism comprising anegative pressure generating groove is provided to a low-pressure side,and a pressure release groove is provided between the positive pressuregenerating groove and negative pressure generating groove, the positivepressure generating groove, pressure release groove, and negativepressure generating groove being communicated with a high-pressure fluidside and separated from a low-pressure fluid side by a seal surface.

A thirteenth aspect of the sliding component of the present invention ischaracterized in that a positive pressure generating mechanismcomprising a positive pressure generating groove is provided to ahigh-pressure side of one of two sliding surfaces that slide relative toeach other in a pair of sliding components, a negative pressuregenerating mechanism comprising a negative pressure generating groove isprovided to a low-pressure side of the other sliding surface, and apressure release groove is provided to each of the one and other slidingsurfaces so as to be positioned between the positive pressure generatinggroove and negative pressure generating groove, the positive pressuregenerating groove, pressure release grooves, and negative pressuregenerating groove being communicated with a high-pressure fluid side andseparated from a low-pressure fluid side by a seal surface.

A fourteenth aspect of the sliding component of the present invention ischaracterized in that an external peripheral side of a pair of slidingcomponents is a high-pressure fluid side, an internal peripheral side isa low-pressure fluid side, a positive pressure generating mechanismcomprising a positive pressure generating groove is provided to ahigh-pressure side of a sliding surface of a stationary-side slidingcomponent, a negative pressure generating mechanism comprising anegative pressure generating groove is provided to a low-pressure sideof a sliding surface of a rotating-side sliding component, and apressure release groove is provided to each of the stationary androtating-side sliding surfaces so as to be positioned between thepositive pressure generating groove and negative pressure generatinggroove, the positive pressure generating groove, pressure releasegrooves, and negative pressure generating groove being communicated withthe high-pressure fluid side and separated from the low-pressure fluidside by a seal surface.

A fifteenth aspect of the sliding component of the present invention ischaracterized in that a pair of sliding components comprise annularbodies, an external peripheral side of the annular bodies is ahigh-pressure fluid side and an internal peripheral side is alow-pressure fluid side; a positive pressure generating mechanismcomprising a positive pressure generating groove is provided to ahigh-pressure side of a sliding surface of the annular body, a negativepressure generating mechanism comprising a negative pressure generatinggroove is provided to a low-pressure side, and a pressure release grooveis provided between the positive pressure generating groove and negativepressure generating groove, the positive pressure generating groove,pressure release groove, and negative pressure generating groove beingcommunicated with the high-pressure fluid side and separated from thelow-pressure fluid side by a seal surface.

A sixteenth aspect of the sliding component of the present invention ischaracterized in that a pair of sliding components comprise annularbodies, an external peripheral side of the annular bodies is ahigh-pressure fluid side and an internal peripheral side is alow-pressure fluid side, a positive pressure generating mechanismcomprising a positive pressure generating groove is provided to ahigh-pressure side in a stationary-side sliding surface of the annularbody, a negative pressure generating mechanism comprising a negativepressure generating groove is provided to a low-pressure side of arotating-side sliding surface of the annular body, and a pressurerelease groove is provided to the stationary and rotating-side slidingsurfaces so as to be positioned between the positive pressure generatinggroove and negative pressure generating groove, the positive pressuregenerating groove, pressure release grooves, and negative pressuregenerating groove being communicated with the high-pressure fluid sideand separated from the low-pressure fluid side by a seal surface.

According to the twelfth through sixteenth aspects, since the slidingsurfaces operate in a state of fluid lubrication during usual timesincluding the start of relative sliding, the frictional coefficient canbe lowered, there is no leakage when no motion is occurring, thepressure gradient ∂p/∂r in the low-pressure side of the sliding surfacecan be made negative during usual times including the start of relativesliding, a pumping action occurs from the low-pressure side of thesliding surface toward the high-pressure fluid side, and the leakagerate can therefore be significantly reduced. Additionally, dynamicpressure generated by the high-pressure-side positive pressuregenerating mechanism can be released to the pressure of thehigh-pressure fluid, the fluid can be prevented from flowing into thelow-pressure-side negative pressure generating mechanism, and thenegative pressure generating performance of the negative pressuregenerating mechanism can be prevented from decreasing.

Furthermore, according to the thirteenth and sixteenth aspects, sincethere is more space than in cases in which both a Rayleigh stepmechanism and a reverse Rayleigh step mechanism are provided to the samesliding surface, the mechanisms are easily disposed in the slidingsurfaces, and machining time can be shortened.

Furthermore, according to the fourteenth aspect described above, thefluid used for lubrication is not susceptible to the effects ofcentrifugal force from rotation, an appropriate amount of fluid can beensured between the sliding surfaces, and a better state of fluidlubrication can therefore be obtained.

A seventeenth aspect of the sliding component of the present inventionis any of the twelfth through sixteenth aspects, characterized in thatcharacterized in that the external-peripheral-side positive pressuregenerating mechanism is formed from a Rayleigh step mechanism, theinternal-peripheral-side negative pressure generating mechanism isformed from a reverse Rayleigh step mechanism, and the pressure releasegroove is formed from a circular groove, the Rayleigh step mechanism,reverse Rayleigh step mechanism, and pressure release groove all beingcommunicated with the high-pressure fluid side via a radial-directiongroove.

According to the seventeenth aspect, in addition to the effects of thetwelfth through sixteenth aspects, the positive pressure generatingmechanism and the negative pressure generating mechanism can easily beprovided to the sliding surfaces of the sliding components.

An eighteenth aspect of the sliding component of the present inventionis the seventeenth aspect, characterized in that pluralities of Rayleighstep mechanisms and reverse Rayleigh step mechanisms are provided inparallel in a circumferential direction to either side of the pressurerelease groove so as to constitute pairs, and an upstream end of agroove part of an n^(th) Rayleigh step mechanism and a downstream end ofa groove part of an n−1^(th) reverse Rayleigh step mechanism are formedso as to substantially coincide in a position in the circumferentialdirection as seen from the upstream side, both groove parts and thepressure release groove being communicated with the high-pressure fluidside via a shared radial-direction groove.

According to the eighteenth aspect, in addition to the effects of theeleventh aspect, Rayleigh step mechanisms and reverse Rayleigh stepmechanisms can be efficiently placed in the sliding surfaces of thesliding components comprising annular bodies, the number ofradial-direction grooves can be reduced, and the fluid leakage rate cantherefore be reduced.

A nineteenth aspect of the sliding component of the present invention isthe seventeenth aspect, characterized in that a plurality of Rayleighstep mechanisms and one reverse Rayleigh step mechanism are provided inparallel in a circumferential direction on either side of the pressurerelease groove, an upstream end of a groove part of one Rayleigh stepmechanism and a downstream end of a groove part of the reverse Rayleighstep mechanism are formed so as to substantially coincide in a positionin the circumferential direction, and the groove parts and the pressurerelease groove are communicated with the high-pressure fluid side via ashared radial-direction groove, the upstream ends of the groove parts ofthe remaining Rayleigh step mechanisms being communicated with thehigh-pressure fluid side via a radial-direction groove of the pressurerelease groove.

According to the nineteenth aspect, in addition to the effects of theseventeenth aspect, the Rayleigh step mechanisms and the reverseRayleigh step mechanism can be efficiently placed in the slidingsurfaces of the sliding components comprising annular bodies, the numberof shared radial-direction grooves can be kept at one, and the fluidleakage rate can therefore be minimized.

A twentieth aspect of the sliding component of the present invention isthe seventeenth aspect, characterized in that a plurality of reverseRayleigh step mechanisms are provided in a radial direction.

According to the twentieth aspect, negative pressure is generatedincrementally, a structure capable of better preventing leakage isachieved, and the invention is therefore applicable to a high-pressureand high-speed seal.

A twenty-first aspect of the sliding component of the present inventionis characterized in that a positive pressure generating mechanismcomprising a spiral groove or a dimple directly communicated with ahigh-pressure fluid side is provided to a high-pressure side of one oftwo sliding surfaces that slide relative to each other in a pair ofsliding components, a negative pressure generating mechanism composed ofa reverse spiral groove is provided to a low-pressure side, and apressure release groove is provided between the spiral groove or dimpleand reverse Rayleigh step mechanism, the pressure release groove andreverse Rayleigh step mechanism being communicated with thehigh-pressure fluid side via a radial-direction groove and separatedfrom a low-pressure fluid side by a seal surface.

A twenty-second aspect of the sliding component of the present inventionis characterized in that a positive pressure generating mechanismcomprising a spiral groove or a dimple directly communicated with ahigh-pressure fluid side is provided to a high-pressure side of one oftwo sliding surfaces that slide relative to each other in a pair ofsliding components, a negative pressure generating mechanism composed ofa reverse spiral groove is provided to a low-pressure side, and apressure release groove is provided between the high-pressure-sidespiral groove or dimple and the low-pressure-side reverse spiral groove,the low-pressure-side reverse spiral groove being communicated with thehigh-pressure fluid side via the pressure release groove and aradial-direction groove and separated from the low-pressure fluid sideby a seal surface.

According to the twenty-first and twenty-second aspects, in addition tothe effects of the twelfth through sixteenth aspects, the positivepressure generating mechanism can be formed from a spiral groove or adimple, and the negative pressure generating mechanism can be formedfrom a reverse Rayleigh step mechanism or a reverse spiral groove.

A twenty-third aspect of the sliding component of the present inventionis any of the third through twenty-second aspects, characterized in thatthe width of the internal-peripheral-side seal surface can be varied.

According to the twenty-third aspect, in cases in which the pressure ofthe sealed fluid is high and other such cases having a high possibilityof leakage, the leakage rate can be reduced by increasing the width ofthe internal-peripheral-side seal surface.

A twenty-fourth aspect of the sliding component of the present inventionis any of the first through twenty-third aspects, characterized in thatthe radial-direction groove is shaped so as to be slanted from theinternal peripheral side communicated with the negative pressuregenerating mechanism to the external peripheral side in the rotationaldirection of the counterpart sliding surface.

According to the twenty-fourth aspect, the same negative pressure effectas with the reverse spiral groove occurs in the radial-direction groove,fluid leaking from the high-pressure side is drawn in, creating anaction of pushing back to the high-pressure fluid side in a state of alessened positive pressure gradient in the radial direction, and leakagefrom the radial-direction groove can therefore be reduced.

Effect of the Invention

The present invention achieves excellent effects such as those below.

(1) According to the first through sixth aspects, there is no leakagewhen no motion is occurring, the pressure gradient ∂p/∂r in thelow-pressure side (the internal peripheral side) of the sliding surfacecan be made negative during usual times including the start of relativesliding, and as a result, Q in formula 1 can be made negative.Specifically, a pumping action occurs from the low-pressure side of thesliding surface toward the high-pressure fluid side, and the leakagerate can therefore be significantly reduced. Furthermore, according tothe third and fifth aspects, since there is more space than in cases inwhich both a Rayleigh step mechanism and a reverse Rayleigh stepmechanism are provided to the same sliding surface, the mechanisms areeasily disposed in the sliding surfaces, and machining time can beshortened.

According to the fourth aspect, the fluid used for lubrication is notsusceptible to the effects of centrifugal force from rotation, anappropriate amount of fluid can be ensured between the sliding surfaces,and a better state of fluid lubrication can therefore be obtained.

(2) According to the seventh aspect described above, in addition to theeffects of (1) described above, the positive pressure generatingmechanism and the negative pressure generating mechanism can be easilyprovided to the sliding surfaces of the sliding components.

(3) According to the eighth aspect described above, in addition to theeffects of (2) described above, the Rayleigh step mechanisms and thereverse Rayleigh step mechanisms can be efficiently placed, the numberof radial-direction grooves can be reduced, and the fluid leakage ratecan therefore be reduced.

(4) According to the ninth aspect described above, in addition to theeffects of (2) described above, the Rayleigh step mechanisms and thereverse Rayleigh step mechanism can be efficiently placed, the number ofshared radial-direction grooves can be kept at one, and the fluidleakage rate can therefore be minimized.

(5) According to the tenth aspect described above, in addition to theeffects of (2) described above, negative pressure is generatedincrementally, a structure capable of better preventing leakage isachieved, and the invention is therefore applicable to a high-pressureand high-speed seal.

(6) According to the eleventh aspect described above, in addition to theeffects of (2) described above, the positive pressure generatingmechanism can be formed from a spiral groove or a dimple.

(7) According to the twelfth through sixteenth aspects described above,in addition to the effects of (2) described above, dynamic pressuregenerated by the high-pressure-side positive pressure generatingmechanism can be released to the pressure of the high-pressure fluid,the fluid can be prevented from flowing into the low-pressure-sidenegative pressure generating mechanism, and the negative pressuregenerating performance of the negative pressure generating mechanism canbe prevented from decreasing.

Furthermore, according to the thirteenth and sixteenth aspects, sincethere is more space than in cases in which both a Rayleigh stepmechanism and a reverse Rayleigh step mechanism are provided to the samesliding surface, the mechanisms are easily disposed in the slidingsurfaces, and machining time can be shortened.

Furthermore, according to the fourteenth aspect described above, thefluid used for lubrication is not susceptible to the effects ofcentrifugal force from rotation, an appropriate amount of fluid can beensured between the sliding surfaces, and a better state of fluidlubrication can therefore be obtained.

(8) According to the seventeenth aspect described above, in addition tothe effects of (6) described above, the positive pressure generatingmechanism and the negative pressure generating mechanism can easily beprovided to the sliding surfaces of the sliding components.

(9) According to the eighteenth aspect described above, in addition tothe effects of (7) described above, Rayleigh step mechanisms and reverseRayleigh step mechanisms can be efficiently placed in the slidingsurfaces of the sliding components comprising annular bodies, the numberof radial-direction grooves can be reduced, and the fluid leakage ratecan therefore be reduced.

(10) According to the nineteenth aspect described above, in addition tothe effects of (6) described above, the Rayleigh step mechanisms and thereverse Rayleigh step mechanism can be efficiently placed, the number ofshared radial-direction grooves can be kept at one, and the fluidleakage rate can therefore be minimized.

(11) According to the twentieth aspect described above, in addition tothe effects of (6) described above, negative pressure is generatedincrementally, a structure capable of better preventing leakage isachieved, and the invention is therefore applicable to a high-pressureand high-speed seal.

(12) According to the twenty-first and twenty-second aspects describedabove, in addition to the effects of (6) described above, the positivepressure generating mechanism can be formed from a spiral groove or adimple, and the negative pressure generating mechanism can be formedfrom a reverse Rayleigh step mechanism or a reverse spiral groove.

(13) According to the twenty-third aspect described above, in cases inwhich the pressure of the sealed fluid is high and other such caseshaving a high possibility of leakage, the leakage rate can be reduced byincreasing the width of the internal-peripheral-side seal surface.

(14) According to the twenty-fourth aspect described above, the samenegative pressure effect as the reverse spiral groove occurs in theradial-direction groove, fluid leaking from the high-pressure side isdrawn in, creating an action of pushing back to the high-pressure fluidside in a state of a lessened positive pressure gradient in the radialdirection, and leakage from the radial-direction groove is thereforereduced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a sliding surface of the sliding component accordingto Embodiment 1 of the present invention, wherein (a) is a plan view ofthe sliding surface and (b) is a perspective view showing an enlargementof part of the sliding surface;

FIG. 2 is a view showing a modification of FIG. 1;

FIG. 3 illustrates a positive pressure generating mechanism composed ofa Rayleigh step mechanism or the like and a negative pressure generatingmechanism composed of a reverse Rayleigh step mechanism or the like,wherein (a) shows a Rayleigh step mechanism, (b) shows a reverseRayleigh step mechanism, (c) and (e) show modified Rayleigh stepmechanisms, and (d) and (f) show modified reverse Rayleigh stepmechanisms;

FIG. 4 illustrates a positive pressure generating mechanism comprising aspiral groove, a positive pressure generating mechanism composed of adimple, and a negative pressure generating mechanism composed of areverse spiral groove, wherein (a) shows the case of a spiral groove,(b) shows the case of a dimple, and (c) shows the case of a reversespiral groove;

FIG. 5 illustrates the results of a numerical analysis of pressuredistribution in the sliding surface of the sliding component accordingto Embodiment 1 of the present invention, wherein (a) is a partialperspective view of the sliding surface and (b) is a pressuredistribution drawing thereof;

FIG. 6 illustrates the sliding surface of the sliding component of thecomparative example, wherein (a) is a plan view of the sliding surfaceand (b) is a perspective view showing an enlargement of part of thesliding surface;

FIG. 7 illustrates the results of a numerical analysis of pressuredistribution in the sliding surface of the sliding component of thecomparative example, wherein (a) is a partial perspective view of thesliding surface and (b) is a pressure distribution drawing thereof;

FIG. 8 illustrates various examples of the numbers and combinations ofRayleigh step mechanisms as positive pressure generating mechanisms andreverse Rayleigh step mechanisms as negative pressure generatingmechanisms according to Embodiment 1 of the present invention;

FIG. 9 illustrates examples of combinations of the spiral groove as apositive pressure generating mechanism and the reverse Rayleigh stepmechanism as a negative pressure generating mechanism according toEmbodiment 1 of the present invention;

FIG. 10 illustrates an example in which a plurality of reverse Rayleighstep mechanisms are provided in the radial direction in a combination ofRayleigh step mechanisms as positive pressure generating mechanisms andreverse Rayleigh step mechanisms as negative pressure generatingmechanisms according to Embodiment 1 of the present invention;

FIG. 11 illustrates an example in which a positive pressure generatingmechanism is provided to one sliding surface, and a negative pressuregenerating mechanism is provided to another sliding surface, inEmbodiment 1 of the present invention;

FIG. 12 is a chart showing the relationship between pressure and leakagerate in the examples (a) through (d) in Embodiment 1 of the presentinvention shown in FIG. 8 and in the comparative example shown in FIG.6;

FIG. 13 illustrates the sliding surface of the sliding componentaccording to Embodiment 2 of the present invention, wherein (a) is aplan view of the sliding surface and (b) is a perspective view showingan enlargement of part of the sliding surface;

FIG. 14 is a drawing showing a modification of FIG. 13;

FIG. 15 illustrates various examples of combinations of Rayleigh stepmechanisms and spiral grooves as positive pressure generatingmechanisms, and reverse Rayleigh step mechanisms and reverse spiralgrooves as negative pressure generating mechanisms, according toEmbodiment 2 of the present invention;

FIG. 16 illustrates an example in which a positive pressure generatingmechanism is provided to one sliding surface and a negative pressuregenerating mechanism is provided to another sliding surface inEmbodiment 2 of the present invention;

FIG. 17 illustrates an example in Embodiment 2 of the present invention,in which a plurality of reverse Rayleigh step mechanisms as negativepressure generating mechanisms are provided in the radial direction;

FIG. 18 shows a modification of FIG. 17, wherein a pressure releasegroove is provided between a plurality of reverse Rayleigh stepmechanisms;

FIG. 19 illustrates an example in Embodiment 2 of the present inventionin which Rayleigh step mechanisms as positive pressure generatingmechanisms and reverse Rayleigh step mechanisms as negative pressuregenerating mechanisms are staggered in the circumferential direction;

FIG. 20 illustrates an example in FIG. 19 in which a plurality ofreverse Rayleigh step mechanisms as negative pressure generatingmechanisms are provided in the radial direction;

FIG. 21 is for describing the sliding surface of the sliding componentaccording to Embodiment 3 of the present invention, wherein (a) is aplan view of the sliding surface and (b) is a perspective view showingan enlargement of part of the sliding surface;

FIG. 22 is a cross-sectional view of a mechanical seal on which ismounted another sliding component paired with the sliding component,according to Embodiment 4 of the present invention; and

FIG. 23 is a cross-sectional view of a thrust bearing on which ismounted another sliding component paired with the sliding component,according to Embodiment 5 of the present invention.

MODE FOR CARRYING OUT THE INVENTION

The best mode for carrying out the sliding component according to thepresent invention is described in detail with reference to the drawings,but the present invention should not be interpreted as being limited tothis mode; various alterations, revisions, and improvements can be madebased on knowledge of those skilled in the art as long as there is nodeviation from the scope of the present invention.

Embodiment 1

FIG. 1 illustrates a sliding surface 2 of a sliding component 1according to Embodiment 1 of the present invention, wherein (a) is aplan view of the sliding surface 2 and (b) is a perspective view showingan enlargement of part of the sliding surface 2.

In FIG. 1, the sliding component 1 is an annular body, wherein usually ahigh-pressure sealed fluid is present on either the internal or externalperiphery of the sliding surface 2 of the sliding component 1, and theother periphery is exposed to the atmosphere.

This sealed fluid can be effectively sealed using the sliding component1. The sliding component 1 is used in both a rotation sealing ring and afixing sealing ring constituting a pair in a mechanical sealing device,for example. The sliding surface of the rotation sealing ring and thesliding surface of the opposing fixing sealing ring are brought in closecontact, and a sealed fluid present on either the internal or externalperiphery of the sliding surface is sealed. The sliding component canalso be used for a bearing that slides against a rotating shaft whilelubricating oil is sealed in one side in the axial direction of acylindrical sliding surface.

In FIG. 1, for the sake of convenience in the description, a case isdescribed in which the high-pressure sealed fluid is present on theexternal periphery.

In FIG. 1, a counterpart sliding component rotates in a counterclockwisedirection relative to the annular body sliding component 1. This holdstrue even if the sliding component 1 rotates in a clockwise direction.

In the sliding surface 2 of the sliding component 1, the externalperiphery is provided with a positive pressure generating mechanism 3composed of a Rayleigh step mechanism, a modified Rayleigh stepmechanism, a spiral groove, a dimple, or another positive pressuregenerating groove; and the internal periphery is provided with anegative pressure generating mechanism 4 composed of a reverse Rayleighstep mechanism, a modified reverse Rayleigh step mechanism, a reversespiral groove, or another negative pressure generating groove.

The positive pressure generating mechanism 3, which is composed of aRayleigh step mechanism, a modified Rayleigh step mechanism, a spiralgroove, a dimple, or another positive pressure generating groove; andthe negative pressure generating mechanism 4, which is composed of areverse Rayleigh step mechanism, a modified reverse Rayleigh stepmechanism, a reverse spiral groove, or another negative pressuregenerating groove; are described hereinafter.

In FIG. 1, a Rayleigh step mechanism is described as an example of thepositive pressure generating mechanism 3, and a reverse Rayleigh stepmechanism is described as an example of the negative pressure generatingmechanism 4.

A plurality of Rayleigh step mechanisms 3 and reverse Rayleigh stepmechanisms 4 are provided in parallel in the circumferential directionso as to constitute pairs and are formed so that as seen from theupstream side, the upstream end of a groove part 5 of an n^(th) Rayleighstep mechanism 3(n) and the downstream end of a groove part 6 of ann−1^(th) reverse Rayleigh step mechanism 4(n−1) substantially coincidein a position in the circumferential direction; and these groove parts5, 6 are communicated with the high-pressure fluid side via a sharedradial-direction groove 7 communicated directly with the high-pressurefluid side. The groove part 5 of the Rayleigh step mechanism 3 and thegroove part 6 of the reverse Rayleigh step mechanism 4 are isolated fromthe low-pressure fluid side by a seal surface 8 on the internalperipheral side. Specifically, the radial-direction groove 7 iscommunicated with the high-pressure fluid side but is not communicatedwith the low-pressure fluid side.

FIG. 2 is a drawing showing a modification of FIG. 1, and in FIG. 2, thesame symbols as FIG. 1 indicate the same members as FIG. 1, and detaileddescriptions are omitted.

In FIG. 2, the means for communicating the groove parts 5, 6 with thehigh-pressure fluid side is different from that of FIG. 1, and acommunication means 50 is configured from a radial-direction groove 51and a communication hole 52 not communicated with the high-pressurefluid side due to the sliding surface 2. Specifically, theradial-direction groove 51 of FIG. 2 is not directly communicated withthe high-pressure fluid side as is the radial-direction groove 7 of FIG.1, but the radial-direction groove 51 itself is formed so as to not becommunicated with the high-pressure fluid side due to the slidingsurface 2, and the groove parts 5, 6 are communicated with thehigh-pressure fluid side by the communication hole 52 joining theradial-direction groove 51 and the high-pressure fluid side. Thecommunication hole 52, being curved at a substantially right angle fromthe radial-direction groove 51 as shown in FIG. 2( b), is designed so asto be communicated with the high-pressure fluid side positioned on theexternal peripheral side of the sliding component 1, but is not limitedto such; it may be provided facing outward at a slant. In cases in whichthe high-pressure fluid side is positioned on the internal peripheralside of the sliding component 1, the communication hole could be formedfacing inward at a slant.

The “positive pressure generating mechanism” and the “negative pressuregenerating mechanism” in the present invention are described herein.

FIG. 3 is for describing a positive pressure generating mechanismcomposed of a Rayleigh step mechanism or another positive pressuregenerating groove and a negative pressure generating mechanism composedof a reverse Rayleigh step mechanism or another negative pressuregenerating groove, wherein (a) shows a Rayleigh step mechanism, (b)shows a reverse Rayleigh step mechanism, (c) and (e) show modifiedRayleigh step mechanisms, and (d) and (f) show modified reverse Rayleighstep mechanisms.

In FIG. 3( a), as shown by the arrows, the sliding component 1 rotatablymoves in a clockwise direction, and another sliding component 10rotatably moves in a counterclockwise direction. In the sliding surface2 of the sliding component 1, a Rayleigh step 9 is formed perpendicularto the relative movement directions and facing upstream, and a groovepart 5 is formed on the upstream side of the Rayleigh step 9. Thesliding surface of the other sliding component 10 is flat.

When the sliding components 1 and 10 move relative to each other in thedirections shown by the arrows, fluid located between the slidingsurfaces of the sliding components 1 and 10 acts due to its ownviscosity as though to follow in the movement direction of the slidingcomponent 1 or 10, at which time dynamic pressure (positive pressure)such as is shown by the dotted lines is therefore generated by thepresence of the Rayleigh step 9.

In FIG. 3( b), as shown by the arrows, the sliding component 1 rotatablymoves in a clockwise direction and another sliding component 10rotatably moves in a counterclockwise direction, but in the slidingsurface 2 of the sliding component 1, a reverse Rayleigh step 11 isformed perpendicular to the relative movement directions and facingdownstream, and a groove part 6 is formed on the downstream side of thereverse Rayleigh step 11. The sliding surface of the other slidingcomponent 10 is flat.

When the sliding components 1 and 10 move relative to each other in thedirections shown by the arrows, fluid located between the slidingsurfaces of the sliding components 1 and 10 acts due to its ownviscosity as though to follow in the movement direction of the slidingcomponent 1 or 10, at which time dynamic pressure (negative pressure)such as is shown by the dotted lines is therefore generated by thepresence of the reverse Rayleigh step 11.

In FIG. 3( c), the Rayleigh step 9 of FIG. 3( a) has been altered inshape to a linear inclined surface 9-1, and in FIG. 3( e), the Rayleighstep 9 of FIG. 3( a) has been altered in shape to a curved inclinedsurface 9-2. With the configurations of FIGS. 3( c) and (e),substantially the same positive pressure as FIG. 3( a) is generated. Inthe present invention, the configurations of FIGS. 3( c) and (e) arereferred to as modified Rayleigh step mechanisms.

In FIG. 3( d), the reverse Rayleigh step 11 of FIG. 3( b) is altered inshape to a linear inclined surface 11-1, and in FIG. 3( f), the reverseRayleigh step 11 of FIG. 3( b) is altered in shape to a curved inclinedsurface 11-2. With the configurations of FIGS. 3( d) and (f),substantially the same negative pressure as FIG. 3( b) is generated. Inthe present invention, the configurations of FIGS. 3( d) and (f) arereferred to as reverse modified Rayleigh step mechanisms.

FIG. 4 is for describing a positive pressure generating mechanismcomprising a spiral groove, a positive pressure generating mechanismcomposed of a dimple, and a negative pressure generating mechanismcomposed of a reverse spiral groove, wherein (a) shows the case of aspiral groove, (b) shows the case of a dimple, and (c) shows the case ofa reverse spiral groove.

The positive pressure generating mechanism of FIG. 4( a), a spiralgroove 12, is provided over the entire periphery of the sliding surfaceon the high-pressure side of the sliding component 1 so as to bedirectly communicated with the high-pressure fluid side. The spiralgroove 12 generates positive pressure by relative rotational motion withthe counterpart sliding surface.

The positive pressure generating mechanism of FIG. 4( b), a dimple 13,is provided over the entire periphery of the sliding surface on thehigh-pressure side of the sliding component 1 without being directlycommunicated with the high-pressure fluid side. The dimple 13 generatespositive pressure by relative rotational motion with the counterpartsliding surface.

The negative pressure generating mechanism of FIG. 4( c), a reversespiral groove 14, is provided over the entire periphery of the slidingsurface of the sliding component 1 without being directly communicatedwith the low-pressure fluid side. The high-pressure side end of thereverse spiral groove 14 is communicated with a pressure release groove15, and part of the pressure release groove 15 is connected to thehigh-pressure fluid side via the radial-direction groove 7. The reversespiral groove 14 is not directly communicated with the low-pressurefluid side, but is isolated by a seal surface. By the relativerotational motion with the counterpart sliding surface, the reversespiral groove 14 acts to generate negative pressure and draw in fluidleaking from the high-pressure-side fluid, and to push the fluid back tothe high-pressure fluid side through the pressure release grooveconnected to the high-pressure fluid side.

In the sliding surface 2 of the sliding component 1 shown in FIGS. 1 and2, eight Rayleigh step mechanisms 3 and reverse Rayleigh step mechanisms4 are provided in parallel in the circumferential direction so as toconstitute pairs. There are many variations of the numbers andcombinations of the Rayleigh step mechanisms 3 and the reverse Rayleighstep mechanisms 4, and preferred examples are described hereinafter.

The depths and widths of the groove parts 5, 6 and the radial-directiongrooves 7, 51, the diameter of the communication hole 52, and the widthof an internal peripheral seal surface 8 are properties that aresuitably determined according to the diameter of the sliding component1, the sliding surface width, the relative movement rate, the conditionsof sealing and lubrication, and other factors.

As one example, in a case in which the diameter of the sliding component1 is approximately 20 mm and the sliding surface width is approximately2 mm, the widths of the groove parts 5 and 6 are 0.4 to 0.6 mm, thedepths are several microns, the width of the internal peripheral sealsurface 8 is 0.2 to 0.4 mm, the width of the radial-direction groove 7(the angle in the circumferential direction) is approximately 6°, andthe depth is several dozen microns.

FIG. 5 shows the results of a numerical analysis of pressuredistribution in the sliding surface of the sliding component accordingto Embodiment 1, wherein (a) is a partial perspective view of thesliding surface and (b) is a pressure distribution drawing.

As shown in FIG. 5( b), positive pressure is generated in the slidingsurface 2, but since the reverse Rayleigh step mechanism 4 is providedin the internal peripheral side, cavitation occurs as a result ofnegative pressure being generated by the reverse Rayleigh step mechanism4. Since the cavitation internal pressure is a negative pressure lowerthan atmospheric pressure, the pressure gradient ∂p/∂r is negative inthe low-pressure-side end, the fluid moves from the high-pressure sideto the low-pressure side, and as a result, drawing in (pumping) occursin the internal peripheral side of the sliding surface. To describe thisphenomenon in further detail, in the low-pressure-side seal surface 8,the pressure in the reverse Rayleigh step mechanism 4 is lower than thelow-pressure-side fluid pressure (atmospheric pressure). As a result,the fluid flows from the constant-pressure fluid side into the reverseRayleigh step mechanism 4 via the low-pressure-side seal surface 8, andas a result of this, drawing in (pumping) occurs in the internalperipheral side of the sliding surface.

To further clarify the effects caused by providing the reverse Rayleighstep mechanism 4 to the internal peripheral side of the sliding surface,an example of a sliding surface not provided with the reverse Rayleighstep mechanism 4 (a comparative example) is shown in FIG. 6.

FIG. 6 is for describing the sliding surface of the comparative example,wherein (a) is a plan view of the sliding surface and (b) is aperspective view showing an enlargement of part of the sliding surface.

In the comparative example, only a Rayleigh step mechanism 3 is providedto the external peripheral side of the sliding surface.

Through relative movement with a counterpart sliding surface, dynamicpressure (positive pressure) is generated by the Rayleigh step mechanism3.

FIG. 7 shows the results of a numerical analysis of pressuredistribution in the sliding component of the comparative example,wherein (a) is a partial perspective view of the sliding surface and (b)is a pressure distribution drawing.

In the case of the comparative example as shown in FIG. 7( b), positivepressure is generated in the sliding surface by the Rayleigh step 9, andthe fluid pressure in the sliding surface is higher than in thelow-pressure fluid side. Specifically, in the internal peripheral end ofthe sliding surface, the pressure gradient ∂p/∂r is positive and thefluid moves from the high-pressure side of the sliding surface to thelow-pressure side; therefore, as a result, leakage occurs from thehigh-pressure fluid side to the low-pressure fluid side.

FIG. 8 shows various examples of the numbers and combinations ofRayleigh step mechanisms 3 as positive pressure generating mechanismsand reverse Rayleigh step mechanisms 4 as negative pressure generatingmechanisms in Embodiment 1 of the present invention.

In FIG. 8( a); there are eight Rayleigh step mechanisms 3 and eightreverse Rayleigh step mechanisms 4, and in FIG. 8( b), there are threeRayleigh step mechanisms 3 and three reverse Rayleigh step mechanisms 4.

In FIG. 8( c) there are three Rayleigh step mechanisms 3 and threereverse Rayleigh step mechanisms 4 and the width w of theinternal-peripheral-side seal surface 8 is doubled, and in FIG. 8( d),there are three Rayleigh step mechanisms 3 and one reverse Rayleigh stepmechanism 4 and the width w of the internal-peripheral-side seal surface8 is doubled.

FIG. 9 shows examples of combinations of the spiral groove 12 as apositive pressure generating mechanism and a reverse Rayleigh stepmechanism 4 as a negative pressure generating mechanism according toEmbodiment 1 of the present invention.

In FIG. 9( a), the spiral groove 12 is provided over the entireperiphery, excluding the portion of the radial-direction groove 7, ofthe high-pressure side of the external peripheral side and is directlycommunicated with the high-pressure fluid, and one reverse Rayleigh stepmechanism 4 is provided to the low-pressure side of the internalperipheral side.

In FIG. 9( b), the spiral groove 12 is provided over the entireperiphery, excluding the portion of the radial-direction groove 7, ofthe high-pressure side of the external peripheral side and is directlycommunicated with the high-pressure fluid, and four reverse Rayleighstep mechanisms 4 are provided to the low-pressure side of the internalperipheral side.

FIG. 10 shows an example in which a plurality of reverse Rayleigh stepmechanisms are provided in the radial direction in a combination ofRayleigh step mechanisms as positive pressure generating mechanisms andreverse Rayleigh step mechanisms as negative pressure generatingmechanisms according to Embodiment 1 of the present invention.

In the sliding surface 2 of the sliding component 1, positive pressuregenerating mechanisms 3 composed of Rayleigh step mechanisms or otherpositive pressure generating grooves are provided in the externalperipheral side, and negative pressure generating mechanisms 4 composedof reverse Rayleigh step mechanisms or other negative pressuregenerating grooves are provided in the internal peripheral side. In FIG.10, there are eight Rayleigh step mechanisms 3 in the externalperipheral side, three rows of internal peripheral reverse Rayleigh stepmechanisms 4 are provided in the radial direction; there are fourradially outer reverse Rayleigh step mechanisms 4-1, two radiallyintermediate reverse Rayleigh step mechanisms 4-2, and one radiallyinner reverse Rayleigh step mechanism 4-3; and eight radial-directiongrooves 7 are provided at equally spaced intervals in thecircumferential direction.

In the case of the present example, since a plurality of reverseRayleigh step mechanisms 4 are provided in the radial direction, theresult is a structure in which negative pressure is generatedincrementally and leakage can be better prevented. Consequently, thisapproach is applicable to high-pressure, high-speed sealing.

FIG. 11 shows an example in which a positive pressure generatingmechanism is provided to one sliding surface, and a negative pressuregenerating mechanism is provided to another sliding surface, inEmbodiment 1 of the present invention.

In FIG. 11, in a pair of sliding components 1-1 and 1-2, a Rayleigh stepmechanism 3 as a positive pressure generating mechanism is provided tothe sliding surface 2-1 of one sliding component 1-1, and a reverseRayleigh step mechanism 4 as a negative pressure generating mechanism isprovided to the sliding surface 2-2 of another sliding component 1-2.

Thus, even in cases in which the Rayleigh step mechanism 3 as a positivepressure generating mechanism and the reverse Rayleigh step mechanism 4as a negative pressure generating mechanism are provided to separatesliding surfaces, there is no leakage when no motion is occurring, thepressure gradient ∂p/∂r of the low-pressure-side ends of the slidingsurfaces can always be made negative including at the start of relativesliding, a pumping action occurs from the low-pressure side of thesliding surface toward the high-pressure fluid side, and the effect ofsignificantly reducing the leakage rate can be achieved, similar tocases in which the Rayleigh step mechanism 3 as a positive pressuregenerating mechanism and the reverse Rayleigh step mechanism 4 as anegative pressure generating mechanism are provided to the same slidingsurface. In addition, since there is more space than in cases in whichthe Rayleigh step mechanism 3 and the reverse Rayleigh step mechanism 4are both provided to the same sliding surface, the mechanisms are moreeasily disposed in the sliding surfaces, and the machining timing can beshortened.

In cases in which the external peripheral sides of the pair of slidingcomponents are the high-pressure fluid sides and the internal peripheralsides are the low-pressure fluid sides, due to positive pressuregenerating mechanisms for actuating the sliding surfaces in a state offluid lubrication being provided to the static sides in the pair ofsliding components 1-1 and 1-2, the fluid used in lubrication is lesssusceptible to the effects of centrifugal force from rotation, anappropriate amount of fluid can be ensured between the sliding surfaces,and a better state of fluid lubrication can therefore be achieved.

FIG. 12 is a chart showing the relationship between pressure and leakagerate in the examples (a) through (d) in the embodiment of the presentinvention shown in FIG. 8 and in the comparative example shown in FIG.6.

The leakage rate of the comparative example was by far the highest, andthe leakage rates of the examples (a) through (d) in the embodimentshown in FIG. 8 was low, from which it is clear that a reverse Rayleighstep mechanism contributes to reducing the leakage rate.

In the examples (a) through (d) in the embodiment shown in FIG. 8, theleakage rate was the lowest in the case of example (d), in which therewere three Rayleigh step mechanisms and one reverse Rayleigh stepmechanism, and the width w of the seal surface on the internalperipheral side was doubled. It is also clear that the leakage rate waslow even at a high pressure in the case of example (c), in which therewere three Rayleigh step mechanisms and three reverse Rayleigh stepmechanisms, and the width w of the seal surface on the internalperipheral side was doubled. In the case of example (a), in which therewere eight Rayleigh step mechanisms and eight reverse Rayleigh stepmechanisms, the leakage rate increased rapidly when the pressureincreased. From the examples described above, it is clear that the fewerthe radial-direction grooves 7 (the fewer the reverse Rayleigh stepmechanisms) and the greater the width w of the seal surface on theinternal peripheral side, the lower the leakage rate.

Embodiment 2

FIG. 13 is for describing the sliding surface 2 of the sliding component1 according to Embodiment 2 of the present invention, wherein (a) is aplan view of the sliding surface 2 and (b) is a perspective view showingan enlargement of part of the sliding surface 2.

In FIG. 13, the same symbols as those of Embodiment 1 indicate the samemembers as Embodiment 1, and detailed descriptions are omitted. In FIG.13, the rotational direction of the counterpart sliding componentopposing the annular sliding component 1 is a counterclockwisedirection. This is the same even if the sliding component 1 rotates in aclockwise direction.

The external peripheral side of the sliding surface 2 of the slidingcomponent 1 is provided with a positive pressure generating groove 3composed of a Rayleigh step mechanism, a modified Rayleigh stepmechanism, a spiral groove, a dimple, or the like; and the internalperipheral side is provided with a negative pressure generatingmechanism 4 composed of a reverse Rayleigh step mechanism, a modifiedreverse Rayleigh step mechanism, a reverse spiral groove, or the like.

The description on FIG. 13 uses a Rayleigh step mechanism as an exampleof a positive pressure generating mechanism 3, and a reverse Rayleighstep mechanism as an example of a negative pressure generating mechanism4.

A pressure release groove 15 is provided between the Rayleigh stepmechanism 3 and the reverse Rayleigh step mechanism 4. The pressurerelease groove 15 is for releasing the dynamic pressure (positivepressure) generated in the high-pressure-side positive pressuregenerating mechanism, e.g., the Rayleigh step mechanism 3 to thepressure of the high-pressure fluid, and thereby preventing fluid fromflowing into the low-pressure-side negative pressure generatingmechanism, e.g., the reverse Rayleigh step mechanism 4 and weakening thenegative-pressure-generating capability of the negative pressuregenerating mechanism. Fluid attempting to flow to the low-pressure fluidside due to the pressure generated in the high-pressure-side positivepressure generating mechanism is led to the pressure release groove 15,which fulfills the role of letting the fluid into the high-pressurefluid side.

The pressure release groove 15 is formed from a circular groove, and isdisposed between the Rayleigh step mechanism 3 and the reverse Rayleighstep mechanism 4 and separated from the two mechanisms by predeterminedsliding surface widths. The depth of the circular groove isapproximately the same depth as the radial-direction groove 7 and thewidth is sufficient to release high pressures, for example, and part ofthe groove is connected to the high-pressure fluid side. In FIG. 13, theRayleigh step mechanism 3, the reverse Rayleigh step mechanism 4, andthe pressure release groove 15 are communicated with the high-pressurefluid side via the radial-direction groove 7, and are separated from thelow-pressure fluid side by the seal surface 8. Specifically, theradial-direction groove 7 communicates the Rayleigh step mechanism 3,the reverse Rayleigh step mechanism 4, and the pressure release groove15 with the high-pressure fluid side but prevents their beingcommunicated with the low-pressure fluid side.

In FIG. 13, a plurality of Rayleigh step mechanisms 3 and reverseRayleigh step mechanisms 4 are provided on either side of the pressurerelease groove 15 so as to be parallel in the circumferential directionand constitute pairs. As seen from the upstream side, the upstream endof the groove part 5 of the n^(th) Rayleigh step mechanism 3 (n) and thedownstream end of the groove part 6 of the n−1^(th) reverse Rayleighstep mechanism 4 (n−1) are formed so as to substantially coincide in aposition in the circumferential direction, and the groove parts 5, 6 andthe pressure release groove 15 are communicated with the high-pressurefluid side via the shared radial-direction groove 7.

FIG. 14 is a drawing showing a modification of FIG. 13, symbols in FIG.14 that are the same as FIG. 13 indicate the same symbols as FIG. 13,and detailed descriptions are omitted.

In FIG. 14, the means for communicating the groove parts 5, 6 with thehigh-pressure fluid side is different from that of FIG. 13, and thecommunication means 50 is configured from the radial-direction groove 51and the communication hole 52 not communicated with high-pressure fluidside by the sliding surface 2. Specifically, the radial-direction groove51 of FIG. 14 is not directly communicated with the high-pressure fluidside as is the radial-direction groove 7 of FIG. 13, theradial-direction groove 51 itself is formed so as to not be communicatedwith high-pressure fluid side by the sliding surface 2, and the grooveparts 5, 6 are communicated with high-pressure fluid side by thecommunication hole 52 that joins the radial-direction groove 51 and thehigh-pressure fluid side. The communication hole 52, being curved at asubstantially right angle from the radial-direction groove 51 as shownin FIG. 14( b), is designed so as to be communicated with thehigh-pressure fluid side positioned on the external peripheral side ofthe sliding component 1, but is not limited to such and may be providedfacing outward at a slant. In cases in which the high-pressure fluidside is positioned on the internal peripheral side of the slidingcomponent 1, the communication hole could be formed facing inward at aslant.

FIG. 15 shows various examples of combinations of Rayleigh stepmechanisms 3 and spiral grooves 12 as positive pressure generatingmechanisms, and reverse Rayleigh step mechanisms 4 and reverse spiralgrooves 14 as negative pressure generating mechanisms, according toEmbodiment 2 of the present invention.

In FIG. 15, the rotational direction of the counterpart sliding surfaceis the same counterclockwise direction as FIG. 13.

In FIG. 15( a), there are eight Rayleigh step mechanisms 3 disposed onthe external peripheral high-pressure side of the sliding component 1and one reverse Rayleigh step mechanism 4 disposed on the internalperipheral low-pressure side, between which the pressure release groove15 is disposed.

In FIG. 15( b), there are eight Rayleigh step mechanisms 3 disposed onthe external peripheral high-pressure side of the sliding component 1and eight reverse Rayleigh step mechanisms 4 disposed on the internalperipheral low-pressure side, between which the pressure release groove15 is disposed.

In FIG. 15( c), there are eight Rayleigh step mechanisms 3 disposed onthe external peripheral high-pressure side of the sliding component 1and a reverse spiral groove 14 provided around the entire periphery ofthe internal peripheral low-pressure side, between which the pressurerelease groove 15 is disposed.

In FIG. 15( d), a spiral groove 12 is provided around the entireperiphery of the external peripheral high-pressure side of the slidingcomponent 1 and one reverse Rayleigh step mechanism 4 is disposed on theinternal peripheral low-pressure side, between which the pressurerelease groove 15 is disposed.

In FIG. 15( e), a spiral groove 12 is provided around the entireperiphery of the external peripheral high-pressure side of the slidingcomponent 1 and eight reverse Rayleigh step mechanisms 4 are disposed onthe internal peripheral low-pressure side, between which the pressurerelease groove 15 is disposed.

In FIG. 15( f), a spiral groove 12 is provided around the entireperiphery of the external peripheral high-pressure side of the slidingcomponent 1 and a reverse spiral groove 14 is provided around the entireperiphery of the internal peripheral low-pressure side, between whichthe pressure release groove 15 is disposed. In this case, the pressurerelease groove 15 fulfills the role of releasing pressure to thehigh-pressure fluid side of the reverse spiral groove 14.

In FIGS. 15( a), (b), (d), and (e), the leakage rate is low in (a) and(d) in which the number of reverse Rayleigh step mechanisms 4 is low.

FIG. 16 shows an example in Embodiment 2 of the present invention, inwhich a positive pressure generating mechanism is provided to onesliding surface and a negative pressure generating mechanism is providedto another sliding surface.

In FIG. 16, among a pair of sliding components 1-1 and 1-2, a Rayleighstep mechanism 3 as a positive pressure generating mechanism is providedto the sliding surface 2-1 of one sliding component 1-1, and a reverseRayleigh step mechanism 4 as a negative pressure generating mechanism isprovided to the sliding surface 2-2 of the other sliding component 1-2.

Thus, even in cases in which a Rayleigh step mechanism 3 as a positivepressure generating mechanism and a reverse Rayleigh step mechanism 4 asa negative pressure generating mechanism are provided to separatesliding surfaces, there is no leakage when no motion is occurring, thepressure gradient ∂p/∂r of the low-pressure-side ends of the slidingsurfaces can always be made negative including at the start of relativesliding, a pumping action occurs from the low-pressure side of thesliding surface toward the high-pressure fluid side, and the effect ofsignificantly reducing the leakage rate can be achieved, similar tocases in which the Rayleigh step mechanism 3 as a positive pressuregenerating mechanism and the reverse Rayleigh step mechanism 4 as anegative pressure generating mechanism are provided to the same slidingsurface. In addition, since there is more space than in cases in whichthe Rayleigh step mechanism 3 and the reverse Rayleigh step mechanism 4are both provided to the same sliding surface, the mechanisms are moreeasily disposed in the sliding surfaces, and the machining timing can beshortened.

In cases in which the external peripheral sides of the pair of slidingcomponents are the high-pressure fluid sides and the internal peripheralsides are the low-pressure fluid sides, due to positive pressuregenerating mechanisms for actuating the sliding surfaces in a state offluid lubrication being provided to the static sides in the pair ofsliding components 1-1 and 1-2, the fluid used in lubrication is lesssusceptible to the effects of centrifugal force from rotation, anappropriate amount of fluid can be ensured between the sliding surfaces,and a better state of fluid lubrication can therefore be achieved.

FIG. 17 shows an example in Embodiment 2 of the present invention, inwhich a plurality of reverse Rayleigh step mechanisms as a negativepressure generating mechanism are provided in the radial direction.

In FIG. 17, in the sliding surface 2 of the sliding component 1, theexternal peripheral side is provided with positive pressure generatingmechanisms 3 composed of Rayleigh step mechanisms or other positivepressure generating grooves, and the internal peripheral side isprovided with negative pressure generating mechanisms 4 composed ofreverse Rayleigh step mechanisms or other negative pressure generatinggrooves. A pressure release groove 15 is provided between the Rayleighstep mechanisms 3 and the reverse Rayleigh step mechanisms 4. Thepressure release groove 15 is for releasing the dynamic pressure(positive pressure) generated in the high-pressure-side positivepressure generating mechanisms, e.g., the Rayleigh step mechanisms 3 tothe pressure of the high-pressure fluid, and thereby preventing fluidfrom flowing into the low-pressure-side negative pressure generatingmechanisms, e.g., the reverse Rayleigh step mechanisms 4 and weakeningthe negative-pressure-generating capability of the negative pressuregenerating mechanisms. Fluid attempting to flow to the low-pressurefluid side due to the pressure generated in the high-pressure-sidepositive pressure generating mechanisms is led to the pressure releasegroove 15, which fulfills the role of letting the fluid into thehigh-pressure fluid side. In FIG. 17, there are eight Rayleigh stepmechanisms 3 in the external peripheral side, three rows of internalperipheral reverse Rayleigh step mechanisms 4 are provided in the radialdirection; there are four radially outer reverse Rayleigh stepmechanisms 4-1, two radially intermediate reverse Rayleigh stepmechanisms 4-2, and one radially inner reverse Rayleigh step mechanism4-3; and eight radial-direction grooves 7 are provided at equally spacedintervals in the circumferential direction.

In the case of the present example, since a plurality of reverseRayleigh step mechanisms 4 are provided in the radial direction, theresult is a structure in which negative pressure is generatedincrementally and leakage can be better prevented. Consequently, thisapproach is applicable to high-pressure, high-speed sealing.

FIG. 18 shows a modification of FIG. 17, wherein a pressure releasegroove is provided between a plurality of reverse Rayleigh stepmechanisms.

In FIG. 18, in the sliding surface 2 of the sliding component 1, theexternal peripheral side is provided with positive pressure generatingmechanisms 3 composed of Rayleigh step mechanisms or other positivepressure generating grooves, and the internal peripheral side isprovided with negative pressure generating mechanisms 4 composed ofreverse Rayleigh step mechanisms or other negative pressure generatinggrooves. In FIG. 18, there are eight Rayleigh step mechanisms 3 in theexternal peripheral side, and three rows of internal peripheral reverseRayleigh step mechanisms 4 are provided in the radial direction; thereare four radially outer reverse Rayleigh step mechanisms 4-1, tworadially intermediate reverse Rayleigh step mechanisms 4-2, and oneradially inner reverse Rayleigh step mechanism 4-3; and eightradial-direction grooves 7 are provided at equally spaced intervals inthe circumferential direction.

Respective pressure release grooves 15 are provided between the Rayleighstep mechanisms 3 and the radially external reverse Rayleigh stepmechanisms 4-1, between the radially external reverse Rayleigh stepmechanisms 4-1 and the radially intermediate reverse Rayleigh stepmechanisms 4-2, and between the radially intermediate reverse Rayleighstep mechanisms 4-2 and the radially internal reverse Rayleigh stepmechanisms 4-3.

Thus, since a plurality of reverse Rayleigh step mechanisms 4 asnegative pressure generating mechanisms are provided in the radialdirection and respective pressure release grooves 15 are providedbetween these mechanisms in the radial direction, negative pressure isgenerated incrementally, and in addition to the effect of betterpreventing leakage, also achieved is the effect of blocking the comingand going of fluid between the reverse Rayleigh step mechanisms 4 andimpeding the occurrence of leakage.

FIG. 19 shows an example in Embodiment 2 of the present invention inwhich Rayleigh step mechanisms as positive pressure generatingmechanisms and reverse Rayleigh step mechanisms as negative pressuregenerating mechanisms are staggered in the circumferential direction.

In FIG. 19, in the sliding surface 2 of the sliding component 1,positive pressure generating mechanisms 3 composed of Rayleigh stepmechanisms or the like are provided in the external peripheral side, andnegative pressure generating mechanisms 4 composed of reverse Rayleighstep mechanisms or the like are provided in the internal peripheralside. FIG. 19 shows a configuration in which there are eight externalperipheral Rayleigh step mechanisms 3 and four internal peripheralreverse Rayleigh step mechanisms 4, and four radial-direction grooves 53communicated with the reverse Rayleigh step mechanisms 4 are provided inpositions that are circumferentially midway between each of the eightradial-direction grooves 7 communicated with the Rayleigh stepmechanisms 3; wherein the Rayleigh step mechanisms 3 as positivepressure generating mechanisms and the reverse Rayleigh step mechanisms4 as negative pressure generating mechanisms are staggered in thecircumferential direction. Pressure release grooves 15 are also providedbetween the Rayleigh step mechanisms 3 and the reverse Rayleigh stepmechanisms 4, and the four radial-direction grooves 53 are communicatedwith the eight radial-direction grooves 7 via the pressure releasegrooves 15. The radial-direction grooves 53 are disposed in the internalperipheral side and are not communicated directly with the high-pressurefluid side, but are communicated with the high-pressure fluid side viathe pressure release grooves 15 and the radial-direction grooves 7.Thus, since the radial-direction grooves 53 communicated with thereverse Rayleigh step mechanisms 4 are not communicated directly withthe high-pressure fluid side but are communicated with the high-pressurefluid side via the narrow pressure release grooves 15, the pressure ofthe radial-direction grooves 53 decreases and leakage from theradial-direction grooves 53 to the static-pressure fluid side isreduced.

FIG. 20 shows an example in FIG. 19 in which a plurality of reverseRayleigh step mechanisms as negative pressure generating mechanisms areprovided in the radial direction.

In FIG. 20, in the sliding surface 2 of the sliding component 1,positive pressure generating mechanisms 3 composed of Rayleigh stepmechanisms or other positive pressure generating grooves are provided inthe external peripheral side, and negative pressure generatingmechanisms 4 composed of reverse Rayleigh step mechanisms or othernegative pressure generating grooves are provided in the internalperipheral side. In FIG. 20, there are eight external peripheralRayleigh step mechanisms 3, three rows of internal peripheral reverseRayleigh step mechanisms 4 are provided in the radial direction, fourradially outer reverse Rayleigh step mechanisms 4-1 are provided, tworadially intermediate reverse Rayleigh step mechanisms 4-2 are provided,and one radially inner reverse Rayleigh step mechanism 4-3 is provided.

Respective pressure release grooves 15 are provided between the Rayleighstep mechanisms 3 and the radially outer reverse Rayleigh stepmechanisms 4-1, between the radially outer reverse Rayleigh stepmechanisms 4-1 and the radially intermediate reverse Rayleigh stepmechanisms 4-2, and between the radially intermediate reverse Rayleighstep mechanisms 4-2 and the radially inner reverse Rayleigh stepmechanism 4-3.

The eight external peripheral Rayleigh step mechanisms 3 arerespectively communicated with the eight radial-direction grooves 7directly communicated with the high-pressure fluid side, the fourradially outer reverse Rayleigh step mechanisms 4-1 are respectivelycommunicated with four radial-direction grooves 54 provided in the samecircumferential formation, the two radially intermediate reverseRayleigh step mechanisms 4-2 are respectively communicated with tworadial-direction grooves 55 provided in the same circumferentialformation, the one radially inner reverse Rayleigh step mechanism 4-3 iscommunicated with one radial-direction groove 56 provided in the samecircumferential formation, and the radial-direction grooves 7, 54, 55,56 of each row are disposed so that their positions are staggered in thecircumferential direction. Therefore, the four radially outer reverseRayleigh step mechanisms 4-1 are communicated with the high-pressurefluid side via the four radial-direction grooves 54 provided in the samecircumferential formation, the pressure release groove 15, and theradial-direction grooves 7; the two radially intermediate reverseRayleigh step mechanisms 4-2 are communicated with the high-pressurefluid side via the two radial-direction grooves 55 provided in the samecircumferential formation, the pressure release groove 15, theradial-direction grooves 54, and the radial-direction grooves 7; and theone radially inner reverse Rayleigh step mechanism 4-3 is communicatedwith the high-pressure fluid side via the one radial-direction groove 56provided in the same circumferential formation, the pressure releasegroove 15, the radial-direction grooves 55, 54, and the radial-directiongrooves 7.

Thus, since the radial-direction grooves 7, 54, 55, 56 are provided ineach row and the radial-direction grooves 7, 54, 55, 56 of each row aredisposed so as to be staggered in the circumferential direction, thehigh-pressure fluid is not directly communicated with the internalperipheral side vicinity of the sliding surface via the radial-directiongrooves, and leakage from the high-pressure fluid side to thelow-pressure fluid side can therefore be better prevented.

Embodiment 3

FIG. 21 is for describing the sliding surface 2 of the sliding component1 according to Embodiment 3 of the present invention, wherein (a) is aplan view of the sliding surface 2 and (b) is a perspective view showingan enlargement of part of the sliding surface 2.

In FIG. 21, the same symbols as those of Embodiments 1 and 2 indicatethe same members as Embodiments 1 and 2, and detailed descriptions areomitted. In FIG. 21, the rotational direction of the counterpart slidingcomponent opposing the annular sliding component 1 is a counterclockwisedirection. This is the same even if the sliding component 1 rotates in aclockwise direction.

In Embodiment 1 described above, the concept that the smaller the numberof reverse Rayleigh step mechanisms 4 (the smaller the number ofradial-direction grooves 7) and the greater the width w of theinternal-peripheral-side seal surface 8, the lower the leakage rate, isas described in Embodiment 1 and so forth. Needless to say, however, thenumber of radial-direction grooves 7 cannot be zero, and there is acertain limit on the width w of the internal-peripheral-side sealsurface 8.

To reduce leakage from the radial-direction grooves 7 in Embodiment 3,whereas in Embodiments 1 and 2 the radial-direction grooves 7 weredisposed in directions of 90° relative to the circumferential direction(the tangential direction), here the grooves are slanted in therotational direction of the counterpart sliding surface and are disposedin a direction of expanding in a radial formation in the rotationaldirection of the counterpart sliding surface, as shown in FIG. 21.

In FIG. 21, in the sliding surface 2 of the sliding component 1,Rayleigh step mechanisms 3 as positive pressure generating mechanismsare provided in the external peripheral side, reverse Rayleigh stepmechanisms 4 as negative pressure generating mechanisms are provided inthe internal peripheral side, and a pressure release groove 15 isprovided between the Rayleigh step mechanisms 3 and the reverse Rayleighstep mechanisms 4.

The groove parts 5 of the Rayleigh step mechanisms 3 and the grooveparts 6 of the reverse Rayleigh step mechanisms 4 are communicated withthe high-pressure fluid side via a shared radial-direction groove 7.

The radial-direction groove 7 is shaped so as to be slanted in therotational direction of the counterpart sliding surface from theinternal peripheral side toward the external peripheral side, and when aplurality of radial-direction grooves 7 are disposed in thecircumferential direction, the grooves are disposed in a direction ofexpanding in a radial formation in the rotational direction of thecounterpart sliding surface.

In the example of the radial-direction groove 7 shown in FIG. 21, thegroove is shaped so as to be slanted in the rotational direction of thecounterpart sliding surface from the internal peripheral sidecommunicated with the groove parts 6 of the reverse Rayleigh stepmechanisms 4 toward the pressure release groove 15 positioned in theexternal peripheral side, and in the portions of the Rayleigh stepmechanisms 3 positioned in the outermost peripheral side of the radialdirection, the groove is shaped facing in a direction 90° relative tothe circumferential direction (the tangential direction). Therefore,fluid that flows from the groove parts 6 of the reverse Rayleigh stepmechanisms 4 into the radial-direction groove 7 is expelled in thedirection shown by the arrow 16.

As shall be apparent, the radial-direction groove 7 may be shaped so asto be uniformly slanted in the rotational direction of the counterpartsliding surface from the internal peripheral side communicated with thegroove parts 6 of the reverse Rayleigh step mechanisms 4 up to theexternal-peripheral-side ends, but essentially the groove is preferablyshaped so as to be slanted in the rotational direction of thecounterpart sliding surface from the internal peripheral side toward theexternal peripheral side.

The greater the slanting angle of the radial-direction groove 7, thelesser the positive pressure gradient in the radial direction in theradial-direction groove 7 (a pressure gradient such that the pressureincreases from the internal peripheral side toward the externalperipheral side), and as a result, the lower the leakage rate from theradial-direction groove 7.

Furthermore, the width of the radial-direction groove 7 may be shaped soas to gradually expand from the internal peripheral side toward theexternal peripheral side.

Thus, due to the radial-direction groove 7 being disposed so as to beslanted in a direction of expanding in a radial formation in therotational direction of the counterpart sliding surface, the internalperipheral side of the radial-direction groove 7 is closed off by theseal surface 8; therefore, the same negative pressure effect as with areverse spiral groove occurs in the radial-direction groove 7, fluidleaking from the high-pressure side is drawn in, creating an action ofpushing back to the high-pressure fluid side in a state of a lessenedpositive pressure gradient in the radial direction, and leakage from theradial-direction groove 7 is therefore reduced.

Embodiment 4

FIG. 22 is a cross-sectional view of a mechanical seal on which ismounted another sliding component paired with the sliding component ofthe present invention.

In a mechanical seal 20, the sliding component 1 of the presentinvention is mounted as a fixing sealing ring 21. The fixing sealingring 21 is movably mounted via an O ring 24 in a holding ring 23 securedto a housing 30. A rotational sealing ring 26, whose sliding surface 29is ground down to a flat surface, is made to face the fixing sealingring 21. The fixing sealing ring 21 creates a seal between an internalside P2 and an atmosphere side P1 while a sliding surface 22 is pressedand held firmly against the opposing sliding surface 29 by a spring 25.In the sliding surface 22 of the fixing sealing ring 21, the externalperipheral side is provided with a positive pressure generatingmechanism 27 composed of a Rayleigh step mechanism, a modified Rayleighstep mechanism, a spiral groove, a dimple, or the like; and the internalperipheral side of the sliding surface 22 is provided with a negativepressure generating mechanism 28 composed of a reverse Rayleigh stepmechanism, a modified reverse Rayleigh step mechanism, a reverse spiralgroove, or the like. The effects achieved by this configuration are thatthere is no leakage when no motion is occurring, the frictionalcoefficient is low because the action of the external peripheralpositive pressure generating mechanism 27 always takes place in a stateof fluid lubrication including the beginning of rotation, and leakagecan be reduced because the internal peripheral negative pressuregenerating mechanism 28 makes pumping possible from the low-pressureside to the high-pressure side. In cases in which the pressure releasegroove (not shown) of Embodiment 2 above is provided between thepositive pressure generating mechanism 27 and the negative pressuregenerating mechanism 28, the dynamic pressure generated by the positivepressure generating mechanism 27 is released to the pressure of thehigh-pressure fluid, whereby the fluid does not flow into thelow-pressure-side negative pressure generating mechanism 28, and loss ofthe negative pressure generating capability of the negative pressuregenerating mechanism can be prevented.

Embodiment 5

FIG. 23 is a cross-sectional view of a thrust bearing on which ismounted another sliding component paired with the sliding component ofthe present invention.

The number 40 indicates an entire thrust bearing, which is basicallyconfigured from a cylindrical housing 44 which is disposed so as toenclose the external peripheral surface of an annular ridged protrusion42 provided to a rotating shaft 41, and which has an internal peripheralsurface that faces the external periphery of the ridged protrusion 42via a minuscule radial-direction gap 43; and thrust receivers 46, 47which extend inward in the radial direction from both ends of thehousing 44 and which face the end surfaces of the ridged protrusion 42via tiny gaps 45 in the thrust direction; the bearing body beingconfigured by the housing 44 and the thrust receivers 46, 47.

The thrust receivers 46, 47 of the bearing body and the end surfaces ofthe ridged protrusion 42 are in rotatable slidable contact with eachother in the axial direction. A lubricant is held by its own surfacetension in the minuscule radial-direction gap 43 and the minusculethrust-direction gaps 45.

Furthermore, the external peripheral sides of the sliding surfaces ofthe thrust receivers 46, 47 are provided with positive pressuregenerating mechanisms 48 composed of Rayleigh step mechanisms, modifiedRayleigh step mechanisms, spiral grooves, dimples, or the like, and theinternal peripheral sides of the sliding surfaces are provided withnegative pressure generating mechanisms 49 composed of reverse Rayleighstep mechanisms, modified reverse Rayleigh step mechanisms, reversespiral grooves, or the like.

The effects achieved by this configuration are that there is no leakagewhen no motion is occurring, the frictional coefficient is low becausethe action of the external peripheral positive pressure generatingmechanisms 48 consistently takes place in a state of fluid lubricationincluding the beginning of rotation, and leakage can be reduced becausethe internal peripheral negative pressure generating mechanisms 49 makepumping possible from the low-pressure side to the high-pressure side.

In cases in which the pressure release grooves (not shown) of Embodiment2 above are provided between the positive pressure generating mechanisms48 and the negative pressure generating mechanisms 49, the dynamicpressure generated by the positive pressure generating mechanisms 48 isreleased to the pressure of the high-pressure fluid, whereby the fluiddoes not flow into the low-pressure-side negative pressure generatingmechanisms 49, and loss of the negative pressure generating capabilityof the negative pressure generating mechanisms can be prevented.

KEY

-   -   1 Sliding component    -   2 Sliding surface    -   3 Positive pressure generating mechanism (Rayleigh step        mechanism)    -   4 Negative pressure generating mechanism (reverse Rayleigh step        mechanism)    -   5 Groove part of Rayleigh step mechanism    -   6 Groove part of reverse Rayleigh step mechanism    -   7 Shared radial-direction groove    -   8 Internal-peripheral-side seal surface    -   9 Rayleigh step    -   10 Opposing sliding component    -   11 Reverse Rayleigh step    -   12 Spiral groove    -   13 Dimple    -   14 Reverse spiral groove    -   15 Pressure release groove    -   16 Arrow indicating fluid-expelling direction    -   20 Mechanical seal    -   21 Fixing sealing ring    -   22 Sliding surface    -   23 Holding ring    -   24 O ring    -   25 Spring    -   26 Rotational sealing ring    -   27 Positive pressure generating mechanism    -   28 Negative pressure generating mechanism    -   29 Sliding surface    -   30 Housing    -   40 Thrust bearing    -   41 Rotating shaft    -   42 Ridged protrusion    -   43 Radial-direction gap    -   44 Housing    -   45 Tiny gap    -   46 Thrust receiver    -   47 Thrust receiver    -   48 Positive pressure generating mechanism    -   49 Negative pressure generating mechanism    -   50 Communication means    -   51 Radial-direction groove    -   52 Communication hole    -   53-56 Radial-direction grooves

1-11. (canceled)
 12. A sliding component characterized in that apositive pressure generating mechanism comprising a positive pressuregenerating groove is provided to an internal high-pressure peripheralside of one of two sliding surfaces that slide relative to each other ina pair of sliding components, a negative pressure generating mechanismcomprising a negative pressure generating groove is provided to anexternal low-pressure peripheral side, and a pressure release groove isprovided between said positive pressure generating groove and negativepressure generating groove, said positive pressure generating groove,pressure release groove, and negative pressure generating groove beingcommunicated with a high-pressure fluid side and separated from alow-pressure fluid side by a seal surface on the external peripheralside.
 13. A sliding component according to claim 12, characterized inthat said pressure release groove is provided to each of said one andother sliding surfaces so as to be positioned between said positivepressure generating groove and negative pressure generating groove. 14.A sliding component characterized in that an external peripheral side ofa pair of sliding components is a high-pressure fluid side, an internalperipheral side is a low-pressure fluid side, a positive pressuregenerating mechanism comprising a positive pressure generating groove isprovided to a high-pressure side of a sliding surface of astationary-side sliding component, a negative pressure generatingmechanism comprising a negative pressure generating groove is providedto a low-pressure side of a sliding surface of a rotating-side slidingcomponent, and a pressure release groove is provided to each of saidstationary-side and rotating-side sliding surfaces so as to bepositioned between said positive pressure generating groove and negativepressure generating groove, said positive pressure generating groove,pressure release grooves, and negative pressure generating groove beingcommunicated with the high-pressure fluid side and separated from thelow-pressure fluid side by a seal surface on the external peripheralside.
 15. A sliding component characterized in that a pair of slidingcomponents comprise annular bodies, an external peripheral side of theannular bodies is a high-pressure fluid side and an internal peripheralside is a low-pressure fluid side, a positive pressure generatingmechanism comprising a positive pressure generating groove is providedto a high-pressure side of a sliding surface on one side of the annularbody, a negative pressure generating mechanism comprising a negativepressure generating groove is provided to a low-pressure side, and apressure release groove is provided between said positive pressuregenerating groove and negative pressure generating groove, said positivepressure generating groove, pressure release groove, and negativepressure generating groove being communicated with the high-pressurefluid side and separated from the low-pressure fluid side by a sealsurface on the external peripheral side.
 16. A sliding componentaccording to claim 15, characterized in that said positive pressuregenerating mechanism comprising a positive pressure generating groove isprovided to a high-pressure side in a stationary-side sliding surface ofthe annular body, said negative pressure generating mechanism comprisinga negative pressure generating groove is provided to a low-pressure sideof a rotating-side sliding surface of the annular body, and a pressurerelease groove is provided to said stationary-side and rotating-sidesliding surfaces so as to be positioned between said positive pressuregenerating groove and negative pressure generating groove, said positivepressure generating groove, pressure release grooves, and negativepressure generating groove being communicated with the high-pressurefluid side and separated from the low-pressure fluid side by a sealsurface on the external peripheral side.
 17. The sliding componentaccording to claim 12, characterized in that theexternal-peripheral-side positive pressure generating mechanism isformed from a Rayleigh step mechanism, the internal-peripheral-sidenegative pressure generating mechanism is formed from a reverse Rayleighstep mechanism, and the pressure release groove is formed from acircular groove, said Rayleigh step mechanism, reverse Rayleigh stepmechanism, and pressure release groove all being communicated with thehigh-pressure fluid side.
 18. The sliding component according to claim17, characterized in that pluralities of Rayleigh step mechanisms n andreverse Rayleigh step mechanisms n are provided in parallel in acircumferential direction to either side of the pressure release grooveso as to constitute pairs, and an upstream end of a groove part of ann^(th) Rayleigh step mechanism and a downstream end of a groove part ofan n−1^(th) reverse Rayleigh step mechanism are formed so as tosubstantially coincide in a position in the circumferential direction asseen from the upstream side, both groove parts and the pressure releasegroove being connected with the high-pressure fluid side via a sharedcommunication groove.
 19. (canceled)
 20. The sliding component accordingto claim 17, characterized in that a plurality of reverse Rayleigh stepmechanisms are provided in a radial direction. 21-22. (canceled)
 23. Thesliding component according to claim 12, characterized in that the widthof the internal-peripheral-side seal surface can be varied.
 24. Thesliding component according to claim 12, characterized in that aradial-direction groove is shaped so as to be slanted from the internalperipheral side communicated with the negative pressure generatingmechanism to the external peripheral side in the rotational direction ofthe counterpart sliding surface.